What is Human Herpesvirus 8?
Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is a member of the herpesvirus family. It is primarily known for its role in causing Kaposi's sarcoma (KS), a type of cancer that forms in the lining of blood and lymph vessels. HHV-8 is also associated with other lymphoproliferative disorders and cancers, such as primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD).
How is HHV-8 Transmitted?
HHV-8 is primarily transmitted through saliva, but it can also be spread through sexual contact, blood transfusion, and organ transplantation. The virus is more prevalent in certain populations, including men who have sex with men and individuals from Mediterranean, African, and Middle Eastern regions.
Kaposi's Sarcoma (KS): This is the most well-known cancer associated with HHV-8. KS is characterized by lesions on the skin, in the mouth, and sometimes in internal organs.
Primary Effusion Lymphoma (PEL): A rare type of non-Hodgkin lymphoma that typically occurs in body cavities such as the pleural, peritoneal, and pericardial spaces.
Multicentric Castleman's Disease (MCD): A rare disorder that involves an overgrowth of cells in the body's lymph nodes.
Latency-Associated Nuclear Antigen (LANA): This viral protein helps the virus evade the host immune system and promotes cell survival and proliferation.
Viral Cyclin: Mimics cellular cyclins to drive the cell cycle forward, leading to uncontrolled cell division.
vIL-6: A viral interleukin-6 homolog that promotes inflammation and angiogenesis, which are critical for tumor growth.
Kaposi's Sarcoma: Lesions that can appear as red, purple, or brown spots on the skin or mucous membranes. Internal KS may cause symptoms like gastrointestinal bleeding or respiratory issues.
Primary Effusion Lymphoma: Symptoms include fluid accumulation in body cavities, shortness of breath, and abdominal swelling.
Multicentric Castleman's Disease: Enlarged lymph nodes, fever, night sweats, and fatigue.
How is HHV-8 Diagnosed?
Diagnosis typically involves a combination of clinical evaluation, imaging studies, and laboratory tests. Specific tests for HHV-8 include:
Polymerase Chain Reaction (PCR): Detects viral DNA in blood or tissue samples.
Serology: Tests for antibodies against HHV-8.
Biopsy: A tissue sample is taken for histological examination to identify characteristic features of HHV-8-associated cancers.
Prevention and Prognosis
Preventing HHV-8 infection involves reducing exposure to known transmission routes. This includes practicing safe sex, screening blood products, and using antiviral prophylaxis in high-risk transplant recipients. The prognosis for HHV-8-associated cancers varies. Early-stage KS may have a good prognosis with appropriate treatment, while advanced PEL and MCD can be more challenging to treat and may have a poorer outlook.
